I looked into this a bit and it seems the very low end estimates are comparing total rockets launched against Iron Dome interceptions, but this is extremely misleading as they don't try to intercept every rocket, only those that are actually headed right at a population center. Most of the rockets land on open ground, and part of the Iron Dome battery is a tracking station that calculates the trajectory of incoming rockets. The Israelis also launch two interceptors at every rocket deemed to be a real threat, so obviously one of those is redundant most of the time. What does seem to be uncontestably true is that the system has stopped (nearly) every single rocket that would have caused major damage to life and property in Israel, and I think that's the most relevant metric for it.